Question

Define homologous pairs, autosomes, and sex chromosomes. (p. 482)

Short answer

Answer: Homologous pairs are two chromosomes that share the same size, shape, and gene distribution, usually containing the same set of genes but with different alleles. Autosomes are chromosomes that do not determine an individual's sex, and in humans, there are 22 pairs of autosomes. Sex chromosomes, on the other hand, are chromosomes that determine an individual's sex in various organisms, with two types, X and Y, found in humans.

Step-by-step solution

Definition of Homologous Pairs

Homologous pairs are two chromosomes that share the same size, shape, and pattern of gene distribution. They typically contain the same set of genes, but may carry different alleles. Homologous pairs are present in diploid cells, where one chromosome in each pair is inherited from one parent and the other from the other parent. During meiosis, homologous pairs of chromosomes pair up, exchange genetic material, and segregate to create haploid daughter cells.

Definition of Autosomes

Autosomes are chromosomes that are not involved in determining the sex of an individual. They are found in all cells, regardless of an individual's sex. In humans, there are 22 pairs of autosomes, numbered from 1 to 22, with chromosome 1 being the largest and chromosome 22 being the smallest. The remaining pair of chromosomes are called the sex chromosomes. Autosomes contain a variety of genes that determine various traits and characteristics other than sex.

Definition of Sex Chromosomes

Sex chromosomes are chromosomes that determine the sex of an individual in various organisms, including humans. There are two types of sex chromosomes, X and Y. In humans, females have two X chromosomes (XX), while males have one X and one Y chromosome (XY). Different combinations of sex chromosomes in other organisms determine their sex according to the specific species. The X chromosome typically contains many functional genes, whereas the Y chromosome is much smaller and has fewer genes, most of which are related to sex determination and male-specific traits.

Key concepts

Homologous Chromosomes

In genetics, homologous chromosomes are pairs of chromosomes found in diploid cells. They have similar size, shape, and genetic structure, housing the same genes in the same order. However, these genes may vary slightly because of different alleles. Alleles are different versions of a gene that can result in variations of a trait such as eye color or height.
During meiosis, a type of cell division that creates reproductive cells (sperm and eggs), homologous chromosomes line up in pairs. This process allows the exchange of genetic material in a phenomenon known as recombination or crossing over. This ensures genetic diversity among offspring.

• Each homologous chromosome comes from one parent.
• They are vital for accurate segregation of genetic material during meiosis.
• They contribute to genetic variability.

Autosomes

Autosomes are chromosomes that are not involved in determining the sex of an organism. In humans, there are 22 pairs of autosomes in each cell. These pairs are numbered from 1 to 22, with chromosome 1 being the largest and chromosome 22 the smallest.
The main function of autosomes is to carry genes essential for various bodily functions and traits unrelated to an organism's sex. For example, they contain genes responsible for eye color, height, and other physical characteristics.

• There are 22 pairs of autosomes in human cells.
• They are the same in both males and females.
• They determine most of an organism's genetic traits.

Sex Chromosomes

Sex chromosomes are specialized chromosomes that determine the sex of an organism. In humans, these are known as the X and Y chromosomes. Females typically have two X chromosomes (XX), while males have one X and one Y chromosome (XY).
The X chromosome is large and contains many genes that influence a variety of traits beyond just sex determination. In contrast, the Y chromosome is smaller and contains fewer genes, most of which are involved in male sex differentiation.

• Females (XX) and males (XY) have different combinations of sex chromosomes.
• The Y chromosome plays a crucial role in male development.
• Other organisms have varying types and numbers of sex chromosomes, depending on the species.